This invention relates to vehicular steering ball joint assemblies. More particularly, the invention relates to the preloading of such assemblies for achieving relatively constant torques on the ball joints over the useful lives of such joints.
A major requirement of ball joints as utilized in steering links and suspension systems is the maintenance of a relatively constant rotating torque over the useful life of the joint. Normally, as the useful life progresses, the rotating torque decreases and steering wheel play and oscillations tend to increase to the detriment of vehicular operation. Attempts to overcome such undesirable torque loss are numerous. For example, coil springs have been employed within the ball socket cavities of joint assemblies to urge bearing members constantly against the ball. Typically, however, the coil spring has a low compressive longitudinal elastic modulus, and the torques consequently cannot be set sufficiently high enough to meet desired values. Not only is there a large reduction of bearing contact load under small changes in part dimensions due to general wear and abrasion, but in the process of manufacture there often results a large deviation in initially set rotating torque values. As a result, ball joints are rarely manufactured with satisfactory consistency in preload torque values.
Moreover, elastomer members formed under injection or insert molding techniques have also been substituted for coil springs to compensate for the small compressive longitudinal elastic modulus of coil springs. However, although the use of elastomer has provided some improvement, manufacturing techniques for achieving consistency in torque values, regardless of tolerance variations in part sizes, have not yet been satisfactory.